1. The labeled atom method enables us to measure the rate of geochemical activity of microorganisms in conditions close to the natural. 2. Experiments with labeled sulfate showed that the hydrogen sulfide in underground waters of the sulfur and oil deposits of Shor -su is of biogenic origin. 3. The oxidation of hydrogen sulfide underground waters in the third and fourth horizons of Shor -Su also takes place with the participation of microorganisms. LITERATURE CITED [1] S.N. Vinogradskii, "Microbiological analysis of soil. Principles of a new method," Microbiology of the Soil [in Russian] (Academy of Sciences USSR Press, 1952), pp. 446-470. [2] S.N. Vinogradskii, "The direct method in the microbiological investigation of soil," Microbiology of the Soil [in Russian] (Academy of Sciences USSR Press, 1952), p. 399. (3] S.N. Vinogradskii, "Principles of ecological microbiology. Conclusion," Microbiology of the Soil [in Russian] (Academy of Sciences USSR Press, 1952), p. 781. 14 [4] S.I. Kuznetsov, "The use of radioactive carbon (C ) in the form of carbon dioxide for determining the relative values of photosynthesis and chemosynthesis in a number of lakes of different types," Collection: Isotopes in Microbiology (in Russian] (Academy of Sciences USSR Press, 1955), p. 126. [5] Iu.I. Sorokin, "Productivity of chemosynthesis in mud deposits: Doklady Akad. Nauk SSSR 103, 5, 875 (1955). [6] M. V. Ivanov, "The use of isotopes in the study of the rate of sulfate reduction in Lake Belovod," Mi krobiologiia 25, 305 (1956).